Soldering iron

ABSTRACT

A soldering iron includes a housing for accommodating therein at least one heating element and a soldering bit which is releasably secured to the housing. The heating element includes a heat-transmitting contact surface provided on an end face thereof which faces the soldering bit. A heat reception surface of said soldering bit is located opposite the contact surface and in direct contact therewith with no intermediate layer therebetween. A temperature sensor is located adjacent the contact surface and between the contact surface and a filament winding of the heating element.

BACKGROUND OF THE INVENTION

The present invention refers to a soldering iron comprising a housingfor accommodating therein at least one heating means, and a solderingbit which is releasably secured to said housing, said heating meansincluding a heat-transmitting contact surface provided on an end facethereof which faces the soldering bit, and a heat reception surface ofsaid soldering bit being located opposite said contact surface.

From practical experience, a soldering iron is, for example, known inthe case of which the heating means and the soldering bit are arrangedin spaced relationship with one another. The air cushion which is,consequently, formed between the heating means and the soldering bitimpairs the transfer of heat between said heating means and saidsoldering bit.

In the case of a further soldering iron which is known from practicalexperience, the heating means and the soldering bit are fixedlyconnected to one another. Although this improves the transfer of heatfrom the heating means to the soldering bit, it makes it impossible toexchange the soldering bit separately for another one, if it is worn ordamaged.

The soldering bit of said soldering iron is provided with a heatreception surface having depressions arranged therein or projectionsarranged thereon. Complementary projections or depressions are arrangedin/on the contact surface on the end face of the heating means.

SUMMARY OF THE INVENTION

With respect to this prior art, it is therefore the object of thepresent invention to improve a soldering iron of the type mentioned atthe beginning in such a way that production of said soldering iron issimple and that, simultaneously, the transfer of heat between thecontact surface and the heat reception surface is optimized.

Due to the fact that the contact surface and the heat reception surfaceare plane-parallel throughout the whole area thereof and include neitherany depressions nor any projections, they are very easy to produce.Furthermore, a heat-conducting, essentially direct contact with nointermediate layer there between exists between said contact surface andsaid heat reception surface, said direct contact optimizing the transferof heat between said surfaces and providing, in combination with theplane-parallel structural design of said surfaces, a backlash-freecontact, which prevents heat-insulating intermediate layers, such as anair cushion, between the contact surface and the heat reception surfaceto a very large extent.

The production of the soldering bit and of the bit holder isadditionally simplified by the fact that these components and,consequently, the contact surface and the heat reception surface areaxially symmetrical with respect to the longitudinal axis of thesoldering bit and of the bit holder, respectively.

In order to permit the soldering bit and the bit holder to be aligned ina simple manner relative to one another, when the soldering bit issecured to the soldering iron by means of the bit holder, the contactsurface and the heat reception surface can be adapted to be rotatedrelative to one another. The rotary displaceability in combination withthe plane-parallel structural design of the contact surface and of theheat reception surface and the direct contact between said surfacesadditionally permit a better elimination of an air cushion which may,for example, exist between said surfaces.

The contact surface and the heat reception surface may have differentcontours. They can be angular or oval. Circular surfaces are preferablyused for the contact surface and the heat reception surface because theycan be rotated relative to one another more easily and because they areless difficult to produce. In this connection, it will also beadvantageous when the two circular surfaces have the same radius. Inthis case, the surfaces will be in full direct contact without onesurface projecting outwardly beyond the other.

When the soldering bit is electroplated, especially the marginal areasof the heat reception surface, which projects normally outwards in theradial direction relative to the rest of the soldering bit, can beprovided with a slightly thicker layer of the material, which is appliedby electroplating, than the area remote from said marginal areas. Inorder to guarantee also in this case an essentially direct contact withno intermediate layer there between the contact surface and the heatreception surface, said heat reception surface can be larger than thecontact surface. In this way, the contact surface will be in directcontact with the heat reception surface only in the area surrounded bythe marginal area. An additional treatment of the heat reception surfaceafter the electroplating process can be avoided in this way. If,however, such an additional treatment is carried out, e.g. by facegrinding or the like, the heat reception surface can, of course, alsohave the same size as the contact surface.

In accordance with a simple embodiment, the heating means can be anelectrically heatable heating element; the heating element end facewhich faces the soldering bit can directly be the contact surface.

In order to optimize the transfer of heat between the heating means andthe soldering bit, at least the contact surface of the heating means orof the heating element can consist of a material for optimizing thetransfer of heat, i.e. a material having a high thermal conductivitycoefficient. Such materials are e.g. copper, silver or the like.

In order to accelerate and optimize the transfer of heat from theheating means to the contact surface, the end portion of the heatingelement, which faces the soldering bit, can be inserted in a sleeveconsisting of a material having a high thermal conductivity coefficient.In this case, the contact surface is formed on an end face of thesleeve, which faces the soldering bit. The transfer of heat from theheating element to the contact surface is accelerated and optimized bysaid sleeve.

The housing of the soldering iron can comprise several parts, a handlesection accommodating, for example, suitable control electronics forcontrolling the temperature of the soldering bit. The handle section isprovided with an insulation, and this permits the soldering iron to beheld. Said insulation prevents a transfer of heat from the heating meansto the outer surface of the handle section.

In this connection, it will be advantageous when the housing comprises abit holder which is releasably secured to the rest of the housing so asto simplify the structural design of the soldering iron. When said bitholder is at its fastening position, it presses the contact surface andthe heat reception surface firmly onto one another so that the directcontact with no intermediate layer there between is established. It willbe advantageous when the bit holder has a sleeve-shaped structuraldesign and defines a bit-holding sleeve in which at least an end portionof the heating element or heating means is arranged, the soldering bitbeing releasably secured to the free end of said bit-holding sleeve.

For establishing—when the bit holder is secured to the rest of thehousing—a direct contact between the heat reception surface of thesoldering bit and the complementary contact surface and for fasteningthe soldering bit to the soldering iron simultaneously in a simplemanner, the free end of the bit-holding sleeve is provided with anopening through which the soldering bit projects, the end of thesoldering bit facing the heating means being provided with an at leastpartially circumferentially extending collar engaging behind an openingedge of the opening. This permits the soldering bit to be passed easilythrough the opening from the interior of the bit holder until its collarcomes into contact with the opening edge. By screwing the bit holderonto the rest of the housing of the soldering iron, or by fastening itin some other way to said housing, the heat reception surface of thesoldering bit is, subsequently, pressed onto the contact surface of theheating means so that said surfaces are in direct contact with eachother.

With regard to the direct contact between the heat reception surface andthe contact surface, reference is additionally made to the fact that thenormal lines associated with these two surfaces can extend parallel toor at an angle to the longitudinal axis of the soldering bit or of thesoldering iron. A rotation of the two surfaces relative to one anotheris given when said normal lines extend parallel to the longitudinalaxes.

The direct contact between the two surfaces and, simultaneously, awobble-free mounting of the soldering bit in the bit holder aresupported by the backlash-free contact between the opening edge and thecollar; said opening edge and said collar can be provided with contactbevels which face each other and which are in contact with each other.

In this connection, it will suffice when the opening edge extendsradially inwards in the direction of the longitudinal axis and when e.g.only the collar is provided with a suitable contact bevel. The combinedeffect of the opening edge and of the contact bevel will provide bothcentering of the soldering bit and wobble-free mounting. Oblique contactbevels can also be dispensed with in this connection, and the openingedge and a complementary contact bevel of the collar can extendessentially at right angles to the longitudinal axis of the solderingbit or of the bit holder.

A retaining projection can project essentially radially outwards beyondthe soldering bit at least at certain locations and in spacedrelationship with the collar so as to prevent the soldering bit frombeing detached from the bit holder when said bit holder is beingreleased. When said bit holder is being released, this retainingprojection can come into contact with the complementary opening edge andprevent the soldering bit from falling into the bit holder too early. Inthis way, the bit holder can be released from the rest of the solderingiron together with the soldering bit.

In accordance with a simple embodiment, the retaining projection can bean annular bead extending around the soldering bit. This annular beadhas an outer diameter which corresponds at least to the inner diameterof the opening of the bit holder. Even if this outer diameter isslightly larger than the inner diameter of the opening, the solderingbit can, in the detached condition of the bit holder, be forced into theinterior of said bit holder and separated therefrom in this way withlittle effort.

In this connection, it will also be advantageous when a groove is formedbetween the retaining projection and the collar, said groove being usedfor receiving therein at least part of the opening edge. The groove canalso extend in the form of an annular groove along the wholecircumference of the soldering bit.

The above-mentioned groove can, for example, also be used for holdingthe soldering bit during the electroplating process. In this connection,said groove can be formed in the soldering bit, in the case of solderingbits with or without retaining projections, in the direction of thefront end of said soldering bit in spaced relationship with the collaror also directly adjacent the collar. In each case, the groove isprovided so as to permit the opening edge of the bit holder to engagesaid groove at least at certain locations or along certain partsthereof. By means of this arrangement, the soldering bit can be held bythe bit holder with the aid of the engagement between the opening edgeand the groove even if the bit holder is detached from the rest of thesoldering iron. It is, of course, also possible to implement the grooveas a circumferential groove extending around the whole bit holder; inthis case, the opening edge can engage the circumferential groove alongthe whole length thereof. The groove can be arranged in an advantageousmanner at least on opposite sides of the soldering bit; in this case,the opening edge engages the groove at these locations.

In this connection, it may also prove to be advantageous when thesoldering bit and/or the bit holder have an essentially oval orelliptical cross-section at least in the area of the groove and/or ofthe opening edge. The groove and the opening edge can lockingly engagein this way, when little pressure is applied thereto. When the solderingbit is being replaced, the soldering bit cannot fall out of the bitholder inadvertently, but the bit holder and the soldering bit locked inposition thereon can be put down and replaced by a different bit holderhaving a suitable soldering bit attached thereto. In addition, worn ordamaged soldering bits can be released from the engagement with theopening edge by light pressure and removed from the bit holder in thisway.

The opening edge engaging the groove and the groove can havecomplementary structural designs so as to permit a positive engagement.Furthermore, it may prove to be advantageous when the opening edgeengages the groove with a certain amount of play, the groove having thena larger cross-section in comparison with the opening edge engaging saidgroove. In addition, the groove can have an asymmetrical cross-sectionwith respect to the radial direction. This asymmetrical cross-sectioncan, for example, be of such a nature that the groove has a contactsurface for the opening edge on the side facing the heat receptionsurface. Said contact surface alone or said contact surface incombination with a contact surface of the collar can serve to fasten thesoldering bit by means of the bit holder. The groove can also bearranged in such a way—i.e. essentially without any distance from thecollar—that the contact bevel or surface of the collar extends up to aninto said groove. If no collar is provided, the soldering bit can alsobe held by the bit holder only by means of the engagement between theopening edge and the groove, and secured to the heating means.

In order to influence the elastic properties of the bit holder in thearea of the opening, it may prove to be advantageous when the bit holderis provided with a notch, which is arranged in spaced relationship withthe opening of said bit holder and which extends essentially at rightangles to the longitudinal axis. This notch can have a U-shaped or aV-shaped cross-section. The notch can be provided on the inner side oron the outer side of the bit holder, whereby a raised portion or adepression will be formed on the outer surface of said bit holder. Inaddition, the notch can have an asymmetrical cross-section, i.e. therespective legs of the U or of the V are inclined at different anglesrelative to a radial direction of the bit holder.

In order to increase the elasticity of the opening edge, the notch ispreferably implemented as a depressed notch which is displaced inwardlyin the direction of the longitudinal axis.

For obtaining in this connection identical elastic propertiessymmetrically with respect to the longitudinal axis, the depressed notchcan be implemented as a circumferential notch extending around the bitholder. When the bit holder is being fastened to the rest of thesoldering iron, this will result in an improved elasticity for the bitholder end arranged above said notch and especially for the opening edgethereof so that the heat reception surface of the soldering bit can bepressed onto the contact surface in full-area contact therewith.

The effect produced by the notch is enhanced when the distance betweenthe notch and the opening is at least equal to the distance between thecontact surface and the opening. This applies to the condition in whichthe bit holder is secured to the soldering iron.

In order to be able to utilize the relative rotational displaceabilityof the heat reception surface and the contact surface when the bitholder is being fastened to the rest of the soldering iron, it will beparticularly advantageous when the frictional engagement existingbetween the opening edge and the collar is stronger than that existingbetween the contact surface and the heat reception surface. This willhave the effect that the soldering bit is moved together with the bitholder when said bit holder is being fastened to the soldering iron, andthat the contact surface and the heat reception surface are rotatedrelative to one another until an intimate direct contact between saidtwo surfaces has been established. In the course of this process, saidsurfaces can be smoothed to a certain extent due to the fact that theyare rotated relative to one another, whereby possibly existing surfaceroughnesses will be ground off.

For controlling the temperature in a simple manner, it will beadvantageous to associate a temperature sensor with the heating meansand/or the soldering bit. If such a temperature sensor is associatedwith the heating means and with the soldering bit, the temperaturegradient along the soldering iron axis can simultaneously be adjustedvia suitable electronic means so that the soldering iron can be used inthe best possible manner.

In order to fasten the bit holder and the soldering bit rapidly to therest of the soldering iron, or in order to detach them rapidly from therest of the soldering iron, a quick-change system can be providedbetween the bit holder and a handle section of the housing. By means ofthe quick-change system that is used especially for the soldering bit,said soldering bit, which is a wearing part, can be replaced easily,said wearing part being reduced to a minimum when the bit is as small aspossible and when it is formed separately from the heating means.

The quick-change system can be realized in different ways.

Said quick-change system can, for example, comprise a threaded flangeattached to said handle section, and a knurled nut rotatably supportedon the bit holder. In accordance with a further embodiment of thequick-change system, there are arranged a flange, which is attached tothe handle section and which is provided with an oblique groove, and atleast one bolt provided in the bit holder and adapted to be guided alongsaid groove. Such a bolt can project on the inner side of a ring whichis rotatably supported on one end of the bit holder.

Furthermore, the quick-change system can comprise a threaded flangeattached to the handle section and a snap-to thread provided on the bitholder. Such a snap-to thread can consist of two parts and it can bespring-loaded in the direction of its open position.

The threads used for screwing together the various parts of thequick-change system can be fine-pitch threads, coarse-pitch threads ormultiple threads. The thread can also be a multiple coarse-pitch threadfor rapid release; said multiple coarse-pitch thread can have a shortangle of rotation and it can be of the self-locking type.

Further respective quick-change systems comprise a hook nut on the bitholder and an obliquely extending clamping nut in the handle section, ora locking element on the bit holder and a counterlocking element on thehandle section. The locking element can consist of teeth and thecounterlocking element can consist of a locking slide member.

Further embodiments of the quick-change system are apparent.

In the case of the various quick-change systems, it may also prove to beadvantageous when the bit holder or the bit-holding sleeve is open onone side thereof at least adjacent its free end.

In order to be able to hold the soldering bit safely, especially whenthe objects to be soldered are small or when the operation to be carriedout must be performed very accurately, it will be advantageous when thesoldering iron can be held at a point which is located as close to thesoldering bit as possible. This can be achieved by the feature that atulip-shaped handle portion, which is conically enlarged in thedirection of the soldering bit, projects from the handle section andsurrounds the bit holder at least partially. The tulip-shaped handleportion essentially serves to extend the handle section in the directionof the soldering bit.

In this connection, an advantageous embodiment can be achieved on thebasis of the features that the tulip-shaped handle portion is supportedon said bit holder and that a quick-change system is provided betweenthe end of said tulip-shaped handle portion which faces the handlesection and said handle section. Analogously to the above-mentioned hooknut, knurled nut or the like, the tulip-shaped handle portion canrotatably be supported on the bit holder. In this connection, it must,however, be taken into account that the frictional engagement betweenthe tulip-shaped handle portion and the bit holder and also between theother quick-change systems and the bit holder must at least be firmenough for entraining the bit holder, whereby the above-mentionedrelative rotation between the contact surface and the heat receptionsurface will be caused, before said bit holder is finally secured to thehandle section. The respective part of the quick-change system providedon the bit holder can also be connected to said bit holder such that itis secured against rotation relative thereto.

In order to realize an electrically heatable heating element in a simplemanner, said heating element can comprise a filament winding, especiallya filament winding that is wound onto a winding carrier. The windingcarrier can be produced from a ceramic material. Furthermore, also theheating element as such can consist of ceramic and a temperature sensorcan be embedded in ceramic material in said heating element. In order toprevent the contact surface and the heat reception surface from scalingor from adhering to one another when the soldering iron is in use, theheat reception surface and/or the contact surface are provided with ametallic blocking layer consisting especially of chromium or nickel. Thebit can preferably consist of copper. The heating element, or at leastthe end face thereof, can consist of silver, the metallic blocking layerpreventing these materials from caking.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the present invention will be described and explainedin detail on the basis of the figures enclosed as drawings, in which

FIG. 1 shows a side view, partly in section, of a front end of asoldering iron;

FIG. 2 shows a soldering iron with a bit holder, partly in section, anda quick-change system;

FIG. 3 shows an enlarged representation of a heating means according toFIG. 2;

FIG. 4 shows a soldering iron with a bit holder, partly in section, anda quick-change system analogously to the soldering iron according toFIG. 2 with a different type of heating means;

FIG. 5 shows an enlarged representation of the heating means accordingto FIG. 4;

FIG. 6 shows a soldering iron with a tulip-shaped handle portion;

FIG. 7 shows an enlarged representation of a second embodiment used forfastening a soldering bit;

FIG. 8 shows an enlarged representation of a third embodiment used forfastening a soldering bit;

FIG. 9 shows an enlarged representation of a fourth embodiment used forfastening a soldering bit;

FIG. 10 shows, partly in section, a side view of a front end of asoldering iron with a second embodiment for a quick-change system;

FIG. 11 shows, partly in section, a side view of a front end of asoldering iron with a third embodiment of a quick-change system;

FIG. 12 shows, partly in section, a side view of a front end of asoldering iron with a fourth embodiment for a quick-change system;

FIG. 13 shows a front view of a further embodiment for a bit holder;

FIG. 14 shows, partly in section, a side view of a front end of asoldering iron with a bit holder according to FIG. 13;

FIG. 15 shows, partly in section, a side view of a front end of asoldering iron with a fifth embodiment of a quick-change system;

FIG. 16 shows a representation according to FIG. 15 where thequick-change system is at the fastening position;

FIG. 17 shows, partly in section, a side view of a front end of asoldering iron with a sixth embodiment for a quick-change system;

FIG. 18 shows, partly in section, a side view of a front end of asoldering iron with a seventh embodiment for a quick-change system;

FIG. 19 shows an enlarged representation of a fifth embodiment used forfastening a soldering bit, similar to the embodiments shown in FIG. 7 to9;

FIG. 20 shows a front view of a soldering iron according to embodimentshown in FIG. 19, and

FIG. 21 shows a front view corresponding to FIG. 20, without anysoldering bit.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows the front end of a soldering iron 1. This soldering ironcomprises a housing 2, only part of which is shown. For example, ahandle section 19 used for holding the soldering iron, cf. e.g. FIG. 2,is not shown.

The housing 2 comprises a bit holder or sleeve 12, the end of said bitholder or sleeve 12 located opposite a soldering bit 4 being adapted tobe screwed onto the rest of the housing, e.g. the handle section, or tobe secured to said rest of the housing in some other way.

The bit-holding sleeve 12 is essentially hollow-cylindrical, and aheating means 3 is arranged in the interior thereof. This heating means3 consists of an electrically heatable heating element 8 and of a sleeve11 which is attached to at least an end portion 10 of the heatingelement 8 and which consists of a material 9 having a high heat-transfercoefficient. The end portion 10 of the heating element 8 can completelyfill the interior of said sleeve 11. The heating element 8 is at leastat its end facing the soldering bit 4 in rear contact with a contactsurface 6 of said sleeve 11, said contact surface 6 being formed on saidsleeve 11 on the end face facing the soldering bit 4.

In FIG. 1, an air gap is shown between a heat reception surface 7 of thesoldering bit 4 and the contact surface 6 of the sleeve 11. This servesto simplify the description of the surfaces in question, the contactsurface 6 and the heat reception surface 7 being in heat-conducting,direct contact with no intermediate layer there between with each otherwhen the bit-holding sleeve 12 is displaced relative to the heatingmeans 3 in the fastening direction 23 so as to secure said bit-holdingsleeve 12 fully to the rest of the housing.

The contact surface 6 and the heat reception surface 7 extendplane-parallel to one another and they are arranged at right angles tothe longitudinal axis 24. In the embodiment shown, said surfaces arecircular and they have identical radii.

The bit-holding sleeve 12 has an opening 13, which is provided at thefree end 14 thereof and beyond which the soldering bit 4 projects. Theopening 13 is surrounded by an opening edge 16 which is bent over in thedirection of the longitudinal axis 24 of the soldering iron or solderingbit. A collar 15 surrounding the heat reception surface 7 at leastpartially engages behind said opening edge 16. The oppositely locatedfront end 22 of the soldering bit 4 has a tapering shape.

Between said collar 15 and the rest of the soldering bit 4, a contactbevel 17 is formed, which extends inwards at an oblique angle towardsthe longitudinal axis 24 and which is in contact with a complementarycontact bevel 18 formed on the inner side of the opening edge 16, cf.e.g. also FIG. 7 to 9.

FIG. 2 shows side view, partly in section, of a soldering iron 1 with ahousing 2. The housing 2 comprises a handle section 19 which is knownper se; the handle section end facing the soldering bit 4 has securedthereto a threaded flange 25 forming a quick-change system 20 togetherwith a knurled nut 26 on the bit holder 12. A further part of thehousing 2 is formed by said bit holder 12 containing the heating means3. The heating means 3 comprises a heating element connection tube 51which extends through said threaded flange 25 and into said handlesection 19. Electric supply lines 53 extend in the interior of saidheating element connection tube 51, said electric supply lines 53 beingused for the electrically heatable heating element 8 as well as for atemperature sensor 42 which is arranged adjacent the contact surface 6in the heating element sleeve 11.

The heating element 8 is defined by a filament winding 40 wound onto aceramic winding carrier 41. The filament winding, the winding carrierand the temperature sensor are surrounded by a ceramic material 52within said sleeve 11.

In the embodiment shown, the heat reception surface 7 and the contactsurface 6 are arranged in spaced relationship with one another, sincethe bit holder 12 has not yet been secured to the handle section 19 bymeans of the quick-change system 20.

FIG. 3 shows an enlarged representation of the heating means 3 accordingto FIG. 2. Identical elements are designated by identical referencesnumerals, and only part of said identical elements is mentioned again.

The heating element connection tube 51 ends in the heating elementsleeve 11 in spaced relationship with the filament winding 40. Theheating element connection tube 51 is filled with ceramic material 52 atleast in the end section thereof.

In contrast to the embodiment according to FIG. 1, the contact bevelsaccording to FIG. 3 are formed at right angles to the longitudinal axis24 and extend radially inwards towards said longitudinal axis.

FIG. 4 shows a further embodiment of a heating means 3. In this case,the winding carrier 41 for the filament winding 40 is surrounded byceramic material 52 also in the direction of the handle section 19. Asfor the rest, reference is made to the description concerning FIGS. 2and 3.

FIG. 5 shows an enlarged representation of the heating means 3 accordingto FIG. 4. Identical elements are again designated by identicalreferences numerals.

In this embodiment, the heating element connecting tube 51 extends up tothe temperature sensor 42 and defines a heating element sleeve 11 whichis open at the end facing the soldering bit 4. This end has arrangedtherein a heat transfer body 57 which surrounds the temperature sensor42 and which is formed of ceramic material integrally with the windingcarrier 41. The heat transfer body 57 is provided with the contactsurface 6 at the end face 5 facing the soldering bit 4. This contactsurface 6 can be formed directly by the end face of said body 57 or by ablocking layer 43 applied to the end face 5 of said body 57.

FIG. 6 shows a further embodiment of the soldering iron having atulip-shaped handle portion 49 arranged on the end of the handle section19 facing the soldering bit 4 or the bit holder 12. This tulip-shapedhandle portion 49 extends from said handle section 19 in the directionof the soldering bit 4 and it has an outwardly enlarging conical shape.Said tulip-shaped handle portion can be formed integrally with thehandle section, or, as shown in the embodiment according to said figure,it can be connected to said handle section 19 via a quick-change system20 at its end 50 facing said handle section 19. With regard to thevarious embodiments for the quick-change system 20, reference is in thisconnection made to the preceding embodiments of the soldering iron andto the explanations concerning FIG. 10 et seq.

FIGS. 7, 8 and 9 show various examples of the manner in which asoldering bit 4 is mounted in the bit holder 12.

In FIG. 7, the soldering bit 4 is provided with a retaining projection44 extending in spaced relationship with the collar 15. This retainingprojection 44 is implemented as a circumferentially extending annularbead merging with the soldering bit via edges extending at an obliqueangle inwards towards the longitudinal axis 24. Between said annularbead 44 and the collar 15, a groove 45 is provided at least part ofwhich is engaged by the opening edge 16.

The contact bevels of the opening edge 16 and of the collar 15, whichabut on one another, are essentially plane-parallel and they extend atright angles to the longitudinal axis 24.

The collar 15 is in direct contact with the contact surface 6 of ablocking layer 43 of the heating element sleeve 11 via its heatreception surface 7.

In FIG. 7, the outer diameter of the circumferential bead 44 isessentially equal to or slightly larger than the inner diameter of theopening edge 16.

In the embodiment according to FIG. 8, no retaining projection 44 isprovided. Instead of a retaining projection, two end bevels 58 areformed on the collar 15, said end bevels 58 extending in the directionof the longitudinal axis 24 and terminating in the heat receptionsurface 7 and in the contact bevel 17, respectively. The contact bevel17 and the complementary contact bevel 18 of the opening edge 16 extendplane-parallel and at right angles to the longitudinal axis 24. Incontrast to the embodiment according to FIG. 7, the bit holder 12according to FIG. 8 is provided with a notch 46 on the outer sidethereof, said notch being formed by a substantially U-shaped depressionin said bit holder 12 in the direction of the longitudinal axis 24. Thedepression extends around the whole bit holder 12 in the form of adepressed or circumferential notch.

The distance 47 between said notch 46 and the opening 13 or the openingedge 16 is larger than the distance 48 between the opening 13 and thecontact surface 6.

In FIG. 9, the collar 15 has only one end bevel 58 between the outersurface of the collar, which faces the bit holder 12, and the heatreception surface 7. A complementary end bevel in the direction of thecontact bevel 17 is not provided. According to FIG. 9, the opening edge13 and the contact bevel 18 formed on the opening-edge bottom side,which faces the collar 15, extend at an oblique angle upwards towardsthe soldering bit 4. Due to this mode of arrangement, an angle is formedbetween the contact bevels or contact surfaces 17 and 18, the openingedge 16 being only in contact with an outer edge of the collar 15.

Also in FIG. 9, a depressed or circumferential notch 46 is formed in thebit holder 12. When seen in a cross-sectional view, the notch issubstantially U-shaped; one leg of said U, which extends in thedirection of the opening edge 16, extending at a larger angle to thelongitudinal axis 24 than the other leg of the U so that the notch hasan asymmetrical shape when seen at right angles to the longitudinal axis24.

In FIGS. 10 to 18, which follow hereinbelow, various embodiments for thequick-change system 20 are shown.

According to FIG. 10, the quick-change system 20 is defined by a hooknut 36 provided with suitable fastening hooks 21 which are adapted to bebrought into engagement with clamping nuts 37 on the inner side of thehandle section 19. The hook nut 36 is rotatably supported on the bitholder 12.

In FIG. 11, the quick-change system 20 comprises a knurled nut 26provided with a helical locking element 38 which is adapted to bebrought into locking engagement with a complementary counterlockingelement 39 provided in the handle section 19. The counterlocking element39 is constructed as a locking slide member.

The knurled nut 26 provided with the thread 38 can, in turn, besupported rotatably on the bit holder 12 or it can be supported suchthat it is secured against rotation relative to said bit holder 12.

In FIG. 12, the quick-change system 20 is defined by a knurled nut 26which is adapted to be screwed onto a flange 25 provided on the handlesection 19, said flange 25 having a coarse-pitch thread 28. Thecoarse-pitch thread can also be implemented as a self-locking multiplethread.

FIG. 13 shows an embodiment of a bit holder 12 which has a lateralopening 55 on one side of the outer surface thereof, said lateralopening 55 being at least provided in the area of the soldering bit 4.

According to FIG. 14, the quick-change system 20 is defined by a knurlednut 26, which is supported on the the bit holder 12, and by a flange 29projecting beyond the handle section 19 and provided with a fine-pitchthread 27.

In the embodiment according to FIGS. 15 and 16, the quick-change system20 comprises a flange 29 arranged on the handle section 19 and providedwith a fine-pitch thread 27, and a two-part snap-to thread 35 supportedon the bit holder 12. In FIG. 15, the two parts of the snap-to threadare spread apart by a spring 56 so that the bit holder 12 can be pushedonto the flange 29.

In FIG. 16, the snap-to thread has been moved into contact with thefine-pitch thread 27 of the flange 29 and the bit holder 12 is securedto the handle section 19. The collar 15 and the heating element sleeve11, or rather the relevant surfaces of these components, cf. thestatements made hereinbefore, are in heat-conducting direct contact withone another.

In FIG. 17, the quick-change system 20 is defined by a knurled nut 26 ora ring 34 suppoted on the bit holder 12. Furthermore, the quick-changesystem 20 includes a flange 29 with a coarse-pitch thread and a groove30, said groove 30 being adapted to have inserted therein two bolts 31,32 on the inner side of the knurled nut 26 and of the ring 34,respectively.

In a last embodiment of the quick-change system 20, said quick-changesystem comprises a knurled nut 26 and a ring 34, which is supported onthe bit holder 12, as well as a flange 29 attached to the handle section19 and provided with obliquely extending grooves 30. In these grooves,bolts 31 and 32 are guided, said bolts projecting on the inner side 33of the bit holder 12 and on the knurled nut 26 and the ring 34,respectively.

In a fifth embodiment used for fastening a soldering bit according toFIG. 19, a groove 45 surrounding the soldering bit 4 is arrangeddirectly adjacent the collar 15. Said groove 45 is engaged by at leastpart of the opening edge 16 of the bit holder 12. Said opening edge 16extends inwards in the radial direction 59, the contact bevel 17 of thecollar 15 extending down to the base 60 of the groove 45. Said base 60of the groove is in this connection asymmetrical with respect to theradial direction 59, i.e. said base of the groove merges e.g. on theside of the collar 15 with the contact bevel 17 extending at rightangles to the longitudinal axis 24 in the case of the embodiment shown.On the opposite side of the groove 45, the base of the groove extends,in the plane of FIG. 19, at an oblique angle to the left up to the outerside of the soldering bit 4.

The groove 45 can also be arranged in spaced relationship with thecollar 15 and, analogously to FIG. 19, said groove 45 can also be inengagement with at least part of an opening edge. In addition, saidgroove 45 can also be used without a collar 15 projecting outwardsbeyond the rest of the soldering bit 4 in the radial direction 59, saidgroove being then used for fastening, by means of the bit holder 12, thesoldering bit directly to the heating element sleeve 11 or directly tothe heating element. Furthermore, the opening edge 16 can also engagesaid groove 45 with a certain amount of play, the soldering bit being inthis case secured in position by means of the bit holder 12 analogouslyto one of the preceding embodiments.

FIG. 20 shows a front view of a soldering bit 4 provided with a bitholder 12 in anlogy with the embodiment according to FIG. 19. It canespecially be seen that the opening edge 16 of the bit holder 12 engagesby means of diametrically opposed insertion-edge portions 61complementary groove portions 62 of the groove 45 according to FIG. 19.The groove 45 may also be provided exclusively in these engagement areasof the insertion-edge portions 61, i.e. it may be limited to said grooveportions 62.

The embodiment according to FIG. 20, additionally shows the feature thatthe soldering bit 4 and the bit holder 12 have an essentially oval orelliptical shape at least in the area of the groove 45 and of theopening edge 16, respectively. The soldering bit 4 and the bit holder 12may also have an oval shape throughout their whole length. Thedimensions of an e.g. elliptical soldering bit 4 and opening edge 16 arepreferably such that a large semiaxis of the soldering bit 4 is largerthan a small semiaxis of the opening edge 16 and smaller than a largesemiaxis of the opening edge 16.

In FIG. 21, the front view according to FIG. 20 is shown in a conditionin which the soldering bit 4 is not inserted. It can especially be seenthat the essentially oval cross-section of the opening 13 of the bitholder 12 is formed by two rounded end portions 63 which areinterconnected by essentially straight insertion-edge portions 61 thatextend parallel to one another. On the whole, the opening 13 has across-section which is point-symmetrical to the longitudinal axis 24.

With regard to the function of the soldering iron according to thepresent invention it is pointed out that an improved heat transfer takesplace between the heating element and the soldering bit, since thecontact surface and the heat reception surface are in direct,heat-transmitting contact with one another throughout their wholesurfaces. Furthermore, the soldering bit is automatically centeredrelative to the heating element and the heating element sleeve,respectively, by the combined effect produced by the opening edge andthe collar of the soldering bit. The intimate direct contact between theheat reception surface and the contact surface is improved still furtherby the fact that the friction between the opening edge and the collar ishigher than that between the contact surface and the heat receptionsurface. This has the effect that, when the bit holder is attached tothe handle section by means of the various quick-change systems, the bitholder will continue to entrain the soldering bit after the firstcontact between said soldering bit and the heating element sleeve, i.e.the soldering bit will be rotated relative to the heating elementsleeve. In this way, an improved heat-transmitting contact will beestablished between the contact surface and the heat reception surface,since said surfaces will be smoothed and air cushions, which may forexample exist between said surfaces, will be eliminated effectively.

What is claimed is:
 1. A soldering iron comprising a housing foraccommodating therein at least one heating means, and a soldering bitwhich is releasably secured to said housing, said heating meansincluding a heat-transmitting contact surface provided on an end facethereof which faces the soldering bit, said heating means furtherincluding a heating element having a filament winding, and a heatreception surface of said soldering bit being located opposite saidcontact surface, the contact surface and the heat reception surfacebeing plane-parallel throughout the whole area thereof andheat-conducting direct contact existing between said contact surface andsaid heat reception surface with no intermediate layer therebetween,characterized in that a temperature sensor is arranged adjacent saidcontact surface and between said contact surface and said filamentwinding of said heating element.
 2. A soldering iron according to claim1, characterized in that the contact surface (6) and the heat receptionsurface (7) are axially symmetrical with respect to the longitudinalaxis (24) of the soldering bit (4).
 3. A soldering iron according toclaim 1 characterized in that the contact surface (6) and the heatreception surface (7) are adapted to be rotated relative to one another.4. A soldering iron according to claim 1, characterized in that thecontact surface (6) and the heat reception surface (7) are circular. 5.The soldering iron of claim 4 wherein said contact surface and saidreception surface have the same radius.
 6. A soldering iron according toclaim 1, characterized in that the heat reception surface (7) has thesame size as or a larger size than the contact surface (6).
 7. Asoldering iron according to claim 1, characterized in that the heatingmeans (3) is an electric heating element (8).
 8. A soldering ironaccording to claim 1, characterized in that at least the contact surface(6) consists of a material (9) for optimizing the transfer of heat.
 9. Asoldering iron according to claim 1, characterized in that the heatingmeans (3) comprises an electric heating element (8) whose end portion(10), which faces the soldering bit (4), is inserted in a heatingelement sleeve (11) consisting of a material (9), for optimizing thetransfer of heat.
 10. The soldering iron of claim 9 wherein saidmaterial of heating element sleeve is silver.
 11. A soldering ironaccording to claim 1, characterized in that the housing (2) comprises abit holder (12) which is releasably secured to the rest of the housingand which has especially the shape of a sleeve, at least an end portionof the heating means (3) being arranged in said bit holder (12), thesoldering bit (4) being releasably secured to the free end (14) of saidbit holder (12).
 12. A soldering iron according to claim 11, whereinsaid free end (14) of said bit holder (12) is provided with an opening(13) through which the soldering bit (4) projects, the end of thesoldering bit (4) facing the heating means (3) being provided with an atleast partially circumferentially extending collar (15) engaging behindan opening edge (16) of said opening (13).
 13. A soldering ironaccording to claim 12, characterized in that the opening edge (16) andthe collar (15) are provided with contact bevels (17, 18) which face oneanother and which abut on one another so as to provide a backlash-freecontact between said opening edge (16) and said collar (15).
 14. Asoldering iron according to claim 12, characterized in that the openingedge (16) extends radially inwards in the direction of a longitudinalaxis (24).
 15. A soldering iron according to claim 12, characterized inthat the opening edge (16) and the contact bevel (17) of the collar (15)extend substantially at right angles to the longitudinal axis (24). 16.A soldering iron according to claim 12, characterized in that aretaining projection (44) projects radially outwards beyond thesoldering bit (4) and that said retaining projection (44) extends inspaced relationship with the collar (15).
 17. The soldering ironaccording to claim 16, wherein said retaining projection comprises anannular bead extending around said soldering bit (4).
 18. A solderingiron according to claim 16, characterized in that a groove (45) isformed between said retaining projection (44) and said collar (15), saidgroove (45) being used for receiving therein at least part of theopening edge (16).
 19. A soldering iron according to claim 12,characterized in that a groove (45) is formed in the soldering bit (4)in the direction of the front end (22) of said soldering bit in spacedrelationship with the collar (15), the opening edge (16) of the bitholder (12) engaging said groove (45).
 20. A soldering iron according toclaim 19, characterized in that the groove (45) is arranged at least onopposite sides of the soldering bit (4).
 21. A soldering iron accordingto claim 19, wherein said soldering bit (4) has a non-circularcross-section at least in the area of said groove.
 22. A soldering ironaccording to claim 17, characterized in that the groove (45) has anasymmetrical cross-section with respect to the radial direction (59).23. The soldering iron according to claim 19 wherein said bit holder(12) has a non-circular cross-section at least in the area of saidopening edge.
 24. A soldering iron according to claim 12 wherein a firstfriction between the opening edge and the collar is more than a secondfriction between the contact surface and the heat reception surface. 25.A soldering iron according to claim 9 wherein said bit holder (12) isopen on one side thereof adjacent said free end.
 26. A soldering ironaccording to claim 11 wherein said housing includes a first tulip-shapedhandle portion that surrounds the bit holder at least partially, saidfirst handle portion conically enlarging in the direction of thesoldering bit.
 27. A soldering iron according to claim 26 wherein saidbit holder supports said first handle portion and further comprising aquick-change system disposed between said first handle portion and asecond handle section.
 28. A soldering iron according to claim 9 whereina first line normal to said contact surface extends parallel to alongitudinal axis of said soldering bit and wherein a second line normalto said heat reception surface extends parallel to a longitudinal axisof said bit holder.
 29. A soldering iron according to claim 1 furthercomprising a bit holder releasably securing said soldering bit to saidhousing and extending along a longitudinal axis, said bit holder havingan opening on one end, said notch arranged in spaced relation to saidopening and extending generally at right angles to said longitudinalaxis.
 30. A soldering iron according to claim 29 wherein said notch isimplemented as a depressed notch which is displaced inwardly in thedirection of the longitudinal axis.
 31. A soldering iron according toclaim 30 wherein said depressed notch is implemented as acircumferential notch extending around the bit holder.
 32. A solderingiron according to claim 29 wherein a first distance between the notchand the opening is at least equal to a second distance between thecontact surface and the opening.
 33. A soldering iron according to claim1, characterized in that said bit holder (12) releasably secures to ahandle section (19) of said housing (2).
 34. A soldering iron accordingto claim 33 wherein said bit holder (12) releasably secures to saidhandle section (19) of said handle section (19) via a threaded flange(25) attached to said handle section (19) and a knurled nut (26)rotatably supported on said bit holder (12).
 35. A soldering ironaccording to claim 33 wherein said bit holder releasably secures to saidhandle section via a flange having an oblique groove therein andattached to said handle section and at least one bolt provided in thebit holder and adapted to be guided along said groove.
 36. A solderingiron according to claim 35 wherein said at least one bolt projects froman inner side of a ring rotatably supported on one end of the bitholder.
 37. A soldering iron according to claim 33 wherein said bitholder releasably secures to said handle section via a threaded flangeattached to the handle section and a snap-to thread provided on the bitholder.
 38. A soldering iron according to claim 37 wherein said snap-tothread comprises two parts spring biased to be open.
 39. A solderingiron according to claim 33 wherein said bit holder releasably secures tosaid handle section via a hook nut on the bit holder and an obliquelyextending clamping nut in the handle section.
 40. A soldering ironaccording to claim 33 wherein said bit holder releasably secures to saidhandle section via a locking element on the bit holder and acounterlocking element on the handle section.
 41. A soldering ironaccording to claim 40 wherein said locking element includes teeth andthe counterlocking element comprises a locking slide member.
 42. Asoldering iron according to claim 33 wherein said bit holder releasablysecures to said handle section of said handle section via a threadedflange having a coarse-pitch thread.
 43. A soldering iron according toclaim 33 wherein said bit holder releasably secures to said handlesection of said handle section via a threaded flange having a multiplethread.
 44. A soldering iron according to claim 1 wherein said heatingelement comprises a filament winding wound onto a winding carrier.
 45. Asoldering iron according to claim 1, characterized in that the heatingelement consists of ceramic and that a temperature sensor (42) isembedded in ceramic material in said heating element (8).
 46. Asoldering iron according to claim 1 wherein at least one of said heatreception surface and said contact surface are formed by a metallicmaterial that includes chromium.
 47. The soldering iron according toclaim 1 wherein at least one of said heat reception surface and saidcontact surface are formed by a metallic material that includes nickel.